Colloidal barium cabonate dispersion and barium soap-barium carbonate grease composition



COLLQEDAL BM CABONATE DISPERSION AND BAUM SOAP-BARIUM CONATE GASECGMPOSHION Herbert Myers, Merchantville, and Ferdinand P. Otto,

Woodbury, NJ, assign'ors to Socony Mobil Oil Company, Inc, a corporationof New York No Drawing. Filed May 20, E959, Ser. No. 814,399

, 3 Claims. (Cl. 252-18) The present invention relates to the productionof colloidal barium carbonate and, more particularly, provides animproved method for producing colloidal suspensions of barium carbonateembodying unique properties by which they are particularly adapted touse in the thickening or gelling of petroleum lubricating oil fractionsfor the production of lubricating greases. The invention also providesthe novel and highly useful colloidal suspensions so produced andimproved lubricating greases produced through the use of our improvedsuspensions.

Lubricating greases have for decades been prepared by thickening apetroleum lubricating oil fraction with a soda or lime soap of a longchain fatty acid, such as oleic acid, palmitic acid or stearic acid, ormixtures thereof, the soap being produced by saponifying the fatty acidpremixed with the oil fraction. More recently, the soaps of other metalshave been used in the manufacture of lubricating greases.

It has, also, more recently, frequently been found desirable' toincorporate in lubricants a substantial amount of an oil-soluble basematerial, sometimes designated reserve base, for the purpose ofneutralizing acidic materials with which the lubricant comes in contactduring use. For this purpose, it has been'proposed to incorporate inlubricating oils an excess of base material as an oilsoluble basic soapor as an oil-soluble complex of -a colloidal alkaline earth metal oxideor carbonate with '21 petroleum sulfonate.

More particularly, it has been proposed to use as the acid-neutralizingagent or detergent in petroleum lubricating oils, an oil-soluble basicsoap or complex of barium carbonate and a sulfonic acid containing asubstantial excess of the carbonate. In the preparation ofthese-oilsoluble salts or complexes, an anhydrous mixture of methanol,mineral oil, barium oxide and an oil soluble or ganic acid or acidsalts, such as sulfonic acid or barium sulfonate, is blown with carbondioxide.

As distinguished therefrom, the present invention is concerned primarilywith the production of lubricating greases consisting essentially of apetroleum lubricating oil fraction thickened to grease consistency byincorporating therein a thickener or gelling agent produced by re- 1acting a long chain fatty acid, for instance stearic acid, with asubstantial excess of colloidal barium carbonate. The invention is moreparticularly directed to the production of a colloidal suspension ofbarium carbonate especially suited to that purpose.

It will be appreciated that, in order to function as a thickening agentfor the mineral oil, for purposes of the present invention, the additivemust be substantially insoluble in the oil. The oil-soluble materials,heretofore proposed as additives for lubricating oil, have been found anot to be effective as thickening or gelling agentsfor the oil to form agrease, especially greases which are stable toward water and are adaptedto use under conditions of high temperature and high bearing loads.

It is, therefore, a primary object of the'present invention-to provide acolloidal suspension of barium carbonate through the use of which theremay be produced greases which, under normal conditions of storage andunder conditions of use at a wide range of temperature 1 conditions, arestable against excessive separation or 3,010,897 Patented Nov. 28, 1961ice bleeding of the mineral oil constituent and which pro- .videsatisfactory lubrication under high temperatures andv cerned, thecolloidal barium. carbonate used must possess a certain characteristics,presently not fully understood, but which may be consistently reproducedby strictadlierence to the conditions herein described and claimed.

We have found that for producing satisfactory greases of the typedescribed, the colloidal suspension of barium carbonate used should notbe formed in the presence of either the fatty acid, or the mineral oil.It further appears that the colloidal suspension so produced should berelatively stable, even in the presence of atmospheric moisture orwater. The size and uniformity of size of the barium carbonate particlesare also believed to be important factors infiuencingthe thickeningproperties of the excess carbonate and avoiding abrasive action. I

It has been proposed, forinstance, to use as a thickening agent ingreases adapted to withstand widely varying temperatures, a colloidaldispersion of calcium carbonate which has been coated by chemicalinteraction with the calcium salt of a low molecular weightpolycarboxylic acid. It has been reported that, for this purpose, a veryspecial mode of preparation of such thickening agents is required. Moreparticularly, it has been reported that the colloidal dispersion of thecalcium carbonate must be prepared in situ in a mixture of the liquidvehicle and an appropriate solvent, and that a dispersing agent mustnecessarily be present during the carbonation in order to obtain: thecarbonate in sufficiently small particle size. Following carbonation,the dicarboxylic 'acid is added to the dispersion to react With-theresultant calcium carbonate. Subsequent removal of the solvents is saidtoproduce' the thickened grease.

According to our present process, the colloidal suspension of thecarbonate is separately prepared, in the ab- .sense of the lubricantvehicle, and no dispersingagent uniform particle size is not obtained.Further, when one attempts to use an excess of the resultant suspensionfor reacting with a fatty acid dispersed in mineral oil to form agrease, there is invariably obtained an unstable mixture from which theoil separated upon standing.

We cannot, at present, state with certainty the characteristic of theresultantcolloidal carbonate which is responsible for thisunsatisfactory result. One may speculate thatthe particle diameter orstructure or surface chemistry or. some combination of thesecharacteristics of the resultant colloidal particles is responsible forthis deficiency. It seems possible that when formed under certainconditions the individual colloidal particles are joined together, afterthe fashion of certain types of carbon black, to form reticulate chainsor clusters which definitely influence'the behavior of the colloid.

v Whatever the cause, we have found that colloidal suspensionsof'bariumcarbonate especially adapted for the purpose herein described and whichare surprisingly stable, even toward water, may be produced by reactingbarium oxide with an excess of anhydrous methylalcoholand'thereaften-adding to the 'resultant'solution, and

uniformly mixing therewith, a minor proportion of Water prior to passingcarbon dioxide gas into the solution.

We have found, more particularly, that the barium oxide must bedissolved completely in the anhydrous methyl alcohol prior to the addingof the water. Water is, of course, readily miscible with methyl alcoholin all proportions. However, when barium oxide is dissolved in themethyl alcohol, a methanol solution of the reaction product is formedwith which water is much less readily miscible. Therefore, precautionshould be taken to assure thorough, uniform mixing of the added waterwith the methanol solution prior to carbonation.

We have found that in the absence of water in the proportion hereinafterdescribed, a waterstable grease, of the type herein described, does notresult from use of the resultant colloidal carbonate. Further, unlesssaid water is throughly mixed with the solution prior to carbonation, wehave been unable to produce a colloidal barium carbonate suspensionsuitable for our present purpose.

Predicated upon these discoveries, the process of our present inventioncomprises the following steps in sequence:

(a) Barium oxide is first reacted with an excess of anhydrous methylalcohol to give a clear solution, filtration being employed, ifnecessary.

(b) A minor proportion of water is then added to the solution, resultingfrom step (a) and is thoroughly stirred into and mixed with thesolution.

Carbon dioxide is then passed into the solution and dissolved therein toconvert the barium oxide-methanol reaction product to bariumbicarbonates. Upon peptization, as by mildly heating, or permitting thesuspension to stand at room temperature for 16 to M hours, a stablecolloidal suspension of barium carbonate results.

The foregoing steps (a), (b) and (c) may, with advantage, be carried outunder ambient conditions of temperature and pressure, thoughcarbonization under-somewhat higher pressure does not appeardeleteriously to affect the characteristics of the resultant suspension.Following the carbonation, the mixture is more advantageously mildlyheated with refluxing, usually at about 153 F. for about 15 minutes,until a substantially clear colloidal solution or suspension isobtained.

In carrying out the process, the proportion of barium oxide reacted withthe anhydrous methyl alcohol maybe varied somewhat. One may, withadvantage, use proportions of barium oxide equivalent to about to aboutbarium, based on the weight of the anhydrous alcohol; however, about12.5% has generally been found to give most satisfactory results.

The proportion of water added to, and mixed with, the resultant solutionof the methanol-barium oxide reaction product, prior to carbonation, hasbeen found to be quite critical. The effective amount of water must bewithin the range of about 1 to about 4 mols of water per mol of bariumpresent in the solution. For most satisfactory results, the proportionof water should be about 2 mols of water per mol of barium. Usingportions of water less than about 1 mol or in excess of about 4 mols permol of barium has not proven satisfactory.

In the carbonation of the methanol-barium oxide reaction product,substantial anhydrous carbon dioxide may be passed through the solutionuntil no more carbon dioxide will dissolve therein. The molar proportionof carbon dioxide thus dissolved must at least equal the mols of bariumpresent and, preferably, should substantially exceed that amount. Wehave, by our present methods, succeeded in dissolving 1.9 mols of carbondioxide per mol of barium present, as against a theoretically possibleratio of 2:1.

Subsequent heating to a temperature of about 153 F. with refluxing, forabout one-quarter hour, has been found to result in a stable,substantially clear solution. Peptization of the solution by longstanding, though permissible, is not presently commercially practical.

The diameter of the resultant colloidal carbonate particles so producedhas been shown by electron microscope examination to be relativelyuniform and to fall within the range from about 0.02 to about 0.2micron.

The following specific examples are included as further detailedillustrations of the invention and should not be construed as limitingthe scope thereof.

Example I Barium oxide was reacted with anhydrous methyl alcohol and thesolution filtered to give a clear solution containing 11.8% barium. To433 grams of the resultant reaction solution, there was added 13 gramsof water. The mixture was then thoroughly stirred until it was entirelyhomogeneous. Carbon dioxide gas was then passed into the mixture atambient temperature and pressure, while periodically weighing the flask,until the molar ratio of the carbon dioxide, thus dissolved, to thebarium present in the mixture was 1:1. The resultant mixture, which wasslightly hazy, was then heated .to about 153 F. with refluxing forone-quarter hour by which time the solution had become only faintlyopalescent.

Example 11 Barium oxide was reacted with anhydrous methyl alco hol andthe solution filtered to give a clear solution containing about 12.5%barium. To the resultant reaction solution, there was added 2 mols ofwater per mol of barium present therein, and the water was thoroughlystirred into the mixture until the mixture was entirely homogeneous.Carbon dioxide gas was then passed into the mixture, as described in thepreceding example, until the mixture was saturated with the carbondioxide and a copious precipitate had formed, the molar ratio of carbondioxide, thus dissolved, to the barium present in the mixture being1.9: 1. Upon heating the resultant mixture for approximately one-quarterhour at about 153 'F., with refluxing, a substantially clear solutionwas obtained.

The colloidal suspensions produced in accordance with the foregoingexamples have been successfully used in the production of stablelubricating greases by mixing the carbonate suspension, a petroleumlubricating oil 'raction and a saturated, straight chain fatty acid invarious proportions and heating the mixture to drive off the methanoland water and effect saponification of the fatty acid.

For example, the suspension resulting from Example I, stearic acid and asolvent refined naphthenic oil, having 9. SUV at 210 F. of 58 seconds,have been used in the following proportions:

Parts by weight Carbonate suspension 22 Petroleum oil 21 Stearic acid 3The resultant mixture was heated with stirring over a period of aboutone hour to a temperature of 190 C. A gel was observed to form shortlyafterthe methanol began coming off and the mixture became thicker andmore crumbly as the temperature increased. Upon cooling, the resultantcrumbly mass was milled to a soft pliable grease.

At ambient temperature, the resultant milled grease exhibited goodmechanical stability, both. dry and in the presence of water, and wasfound to maintain its grease structure at temperatures as high as 250 C.The grease was found to pass the four-ball weld test at a loading ofwithin the range of kilograms, thus showing improved ex-treme pressureproperties.

Barium greases having comparable softening points and similarlyprepared, except that conventional barium carbonate is used instead ofthe colloidal suspension of the present invention, have been found tohave a four-ball weld test value not exceeding 120 kilograms and toexhibit excessive oil leakage when subjected to the A.S.T.M. wheelhearing test.

The four-ball weld tests, referred to above, were carried out inaccordance with the procedure and equipment described in Method 6503 ofFederal Test Method Standard No. 791.

Though the invention has been particularly described and illustratedwith reference to grease manufacture, it will be understood that theutility of the invention is not restricted to the manufacture of greasebut includes other uses where a stable colloidal suspension of bariumcarbonate is indicated.

We claim:

1. Process for producing colloidal suspensions of barium carbonate whichcomprises the following steps, reacting barium oxide with anhydrousmethyl alcohol to form a clear solution containing from about 10% toabout barium, based on the weight of the anhydrous alcohol, thereafteradding to and thoroughly mixing with the resultant solution an amount ofwater within the range of about 1 mol to about 4 mols of water per molof barium, with stirring to form a homogeneous solution, then dissolvingcarbon dioxide in the resultant solution in a molar proportion at leastequal to the mols of barium present therein and heating the resultantmixture with refluxing until a substantially clear colloidal solution isobtained.

2. Process for producing colloidal suspensions of barium carbonate whichcomprises the following steps,

reacting barium oxide with anhydrous methyl alcohol, to

form a clear solution containing about 12.5% barium, based on the weightof the anhydrous alcohol, thereafter adding to and thoroughly mixingwith the resultant solution approximately 2 mols of Water per mol ofbarium present, with stirring to form a homogeneous solution, thensaturating the resultant solution with carbon dioxide and heating theresultant mixture with refluxing until a substantially clear colloidalsolution is obtained.

3. A lubricating grease consisting essentially of a petroleumlubricating oil fraction thickened to a grease consistency with anadmixture of a barium soap of -a long chain fatty acid and colloidalbarium carbonate, said grease having a four-ball weld test value of atleast kilograms.

References Cited in the file of this patent UNITED STATES PATENTS1,884,082 Miller Oct. 25, 1932 FOREIGN PATENTS 478,187 Great BritainJan. 10, 1938 790,473 Great Britain Feb. 12, 1958

3. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF A PETROLEUMLUBRICATING OIL FRACTION THICKENED TO A GREASE CONSISTENCY WITH ANADMIXTURE OF A BARIUM SOAP OF A LONG CHAIN FATTY ACID AND COLLOIDALBARIUM CARBONATE, SAID GREASE HAVING A FOUR-BALL WELD TEST VALUE OF ATLEAST 150 KILOGRAMS.